Ma Xiaoguang, spokesman for the Taiwan Affairs Office of the State Council, said the mainland's quality watchdog is still examining import records to find out whether products produced with the tainted oil have been imported, and it will remove them from shelves immediately if discovered.

"We hope the two sides will further enhance cooperation during the investigation process to protect the health of people," Ma said at a news conference.

The General Administration for Quality Supervision, Inspection and Quarantine made public on Saturday a complete list of companies in Taiwan that were confirmed or suspected to have used the oil, and warned consumers against products made by those companies.

The Shanghai Food and Drug Administration said on Tuesday that it removed more than 8,700 food products from shelves after the tainted oil scandal broke in Taiwan. The authority said retailers must provide certificates of safety if they plan to sell food products produced in Taiwan.

The Guangdong Entry-Exit Inspection and Quarantine Bureau also issued a notice on Tuesday that required quarantine authorities in the province to step up checks to prevent any tainted food products from Taiwan from crossing the border.

Meanwhile, the island's food and drug administration said on Wednesday that health authorities in Kaohsiung fined Chang Guann Co $1.67 million for peddling lard that was tainted with recycled waste oil. The authority also froze the bank account of the deputy general manager of the company.

The cooking oil supplier in Taiwan purchased the recycled oil to produce 782 tons of lard. Some 1,020 food companies and restaurants, including a number of leading brands, were thought to have used the tainted lard.

The administration said Chang Guann imported industrial lard from Hong Kong beginning in 2008 and has so far imported 2,385 metric tons.

The island's public health authority said on Monday that the tainted lard met safety standards. However, since refining recycled oil into lard is against the law, all products made with the adulterated oil should be removed from shelves, it said.

The use of tainted oil, including gutter oil, has been a long-standing food safety problem on the mainland.

In 2011, a special campaign by the Ministry of Public Security confiscated more than 60,000 tons of tainted oil in more than 120 cases. In another raid, the police in Chongqing seized more than 80 tons of gutter oil.

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Li Wenfang in Guangzhou contributed to this story.